Here is a link to a fb group that posted the same as yours and calling them fossilized clams.
That's a good suggestion. I'll try it. Thanks.
Put these pictures in the fb group Texas Rocks and Fossils - very helpful group.
It's very possible, and looks a lot like the pictures I see of bivalves found in Texas. It just looked thinner than I'd expected a bivalve to be. Attached are pictures with a ruler for scale.
Sara, I believe the item you brought to the meeting is a fossilized bivalvia, but there different kinds. I just did a search for fossilized bivalves and came up with many different types. I would suggest doing a search and see which image is of closest resemblance to yours.